Synergistic nematocidal compositions

ABSTRACT

A method for suppressing plant damage by nematodes which comprises the concurrent administration, to the locus, soil or seeds of plants in need of such treatment, of (a) a metabolite of the fungus Myrothecium verrucaria and (b) a chemical pesticide, as well as synergistic nematocidal compositions useful therein.

This application is a continuation application of U.S. Ser. No.08/435,703, filed May 5, 1995, now abandoned.

FIELD OF THE INVENTION

The present invention relates to nematocidal compositions useful in thecontrol of agricultural pests. More particularly, the invention relatesto synergistic combinations of a biopesticide obtained from the fungusMyrothecium verrucaria and a chemical pesticide, in which the chemicalpesticide is applied at a rate substantially lower than that used whenapplied alone. The invention also relates to the use of suchcompositions and/or the concurrent administration of the abovebiopesticide and a chemical pesticide to effectively suppress nematodedamage.

BACKGROUND OF THE INVENTION

Plant parasitic nematodes such as those belonging to the generaMeloidogyne, Heterodera, Pratylenchus and Xiphinema cause billions ofdollars of damage each year to agronomic crops, vegetables, fruits,flowering trees and shrubs. Almost all major plant species aresusceptible to infection by these pests, which typically affect theroots of host plants but also can damage above-ground parts includingthe stem, leaves and flowers. There is consequently a great need forcontrol of these parasites, which in the past has been accomplished bythe administration of chemical nematocides (such as 1,3-dichloropropene;2,3-dihydro-2,2-dimethyl-7-benzofuranyl methylcarbamate; ethyl3-methyl-4-(methylthio)phenyl-(1-methylethyl) phosphoramidate; andmethyl N',N'-dimethyl-N-[(methylcarbamoyl)oxy]-l-thiooxamidimidate).Such compounds can be highly effective; however, many have been found topose an environmental hazard, and in some instances the amount and/orfrequency of use of such compounds has been limited by regulatoryauthorities with the result that their nematocidal effectiveness iscompromised.

As a result, efforts have been made to identify effective means ofsuppressing nematode damage which avoid or reduce the use of chemicalpesticides. One approach has been to employ, in place of chemicalpesticides, nematocides of biological origin with specific modes ofaction and relatively safer toxicological profiles. Examples of suchalternative nematocides include ABG-9008 (a metabolite of the fungusMyrothecium verrucaria, disclosed and claimed in U.S. Pat. No.5,051,255, issued Sep. 24, 1991), and a combination of avermectins (orrelated compounds such as milbemycins) with fatty acids (as disclosedand claimed in U.S. Pat. No. 5,346,698, issued Sep. 13, 1994). Anotherapproach has been to combine spores of Pasteuria penetrans, a bacterialparasite of nematodes, with organophosphate nematicides (as disclosed inAustralian Patent No. 60573/86, published Jan. 29, 1987). However, thepreparation of P. penetrans spores on an industrial scale is hampered bythe fact that the organism is an obligate parasite and therefore must begrown on nematodes in situ and isolated from nematode-infested rootdigests. There remains, therefore, a need for improved means of nematodecontrol which, if involving the use of chemical pesticides, provide fora substantial reduction in the amount of chemical used.

SUMMARY OF THE INVENTION

It has now been found that by combining one or more metabolites producedby the fermentation of M. verrucaria with a chemical pesticide,effective suppression of nematodes is possible at pesticide levels farbelow those needed when the pesticide is applied alone. Surprisingly,the combined effect is synergistic rather than merely additive, in thatnematode control is possible by using application rates below thosenormally required for activity of both the metabolite and the pesticide.

Accordingly, in one aspect of the present invention, a method isdisclosed for the suppression of plant damage by nematodes which methodcomprises the concurrent administration, to the locus, soil or seeds ofplants in need of such treatment, of (a) a metabolite of the fungusMyrothecium verrucaria and (b) a chemical pesticide. These two agentsmay be regarded as having been administered "concurrently" when appliedeither simultaneously (as in the form of a composition in which theagents are combined), or separately (but to the same plants or soil, ina manner such that both are present and active at the same time).

The metabolite used herein may be in the form of an entire culturemedium (including mycelium) obtained by culturing a fungus of thespecies M. verrucaria. Alternatively, the metabolite may be one or moreparticular fractions or components isolated from such a culture medium,extracted and purified according to procedures well-known in the art. Itis also to be expected that such a component, upon elucidation of itsstructural formula, could be synthesized de novo using known chemicalmethods. By "metabolite" as used herein is meant any of the above;however, the metabolite of the present invention is preferably awhole-culture preparation obtained by fermentation and heat-killing ofM. verrucaria, and in particular of M. verrucaria strain ATCC 46474.

It is expected that the nematocidal activity of a wide range of chemicalpesticides may be potentiated by concurrent administration with theabove metabolite. Preferred among the pesticides of the presentinvention, however, are organophosphate and carbamate pesticides.Representative chemical pesticides useful in the claimed method includemethyl propiolate, fenamiphos and oxamyl.

In each case above, it is preferred that the method of the presentinvention be carried out by administering the metabolite and thepesticide in quantities which, when administered alone, would beinsufficient to control nematodes effectively. By "effective control" ismeant a reduction of plant damage such that nematocidal treatment iscost-effective and sufficient to avoid significant economic loss withoutadditional nematode suppression. Specifically, it is preferred that thechemical pesticide be administered at a rate of no more than 50% of therecommended rate (the "label rate" stated on the product packaging andapproved by applicable governmental regulatory agencies) at which thepesticide alone is used in the control of nematodes. Especiallypreferred is a method in which the pesticide and metabolite areadministered at rates of no more than 50% and 75% of their respectivelabel rates for use of each agent alone.

In another preferred embodiment of the above method, the chemicalpesticide is administered at a rate of between about 1% and about 30% ofthe rate recommended for use of the pesticide alone in the control ofnematodes. Especially preferred, and regarded as the best modecontemplated for carrying out the invention, is the method in which thepesticide (at between about 1% and about 30% of the label rate) isapplied concurrently with the metabolite administered at a rate of about50% of the label rate for use of the metabolite alone.

In a further aspect of the present invention, nematocidal compositionsare disclosed which comprise a metabolite of the fungus Myrotheciumverrucaria in combination with a chemical pesticide. A particular suchcomposition is one in which the fungus is Myrothecium verrucaria strainATCC 46474. Preferred among these compositions are those in which thepesticide is an organophosphate pesticide or a carbamate pesticide; morespecifically, preferred compositions include those in which thepesticide is selected from methyl propiolate, fenamiphos and oxamyl.

DETAILED DESCRIPTION OF THE INVENTION

A metabolite of Myrotheciwn verrucaria suitable for use in the methodand compositions of the present invention is that obtained byfermentation of the M. verrucaria strain ATCC 46474; such a metaboliteis commercially available as the bionematocidal product ABG-9008 fromAbbott Laboratories (North Chicago, ill.). The preparation of thismetabolite is also described in detail in U.S. Pat. No. 5,051,255,incorporated herein by reference.

Representative of the organophosphate chemical pesticides useful in thepresent invention is fenamiphos, or ethyl 3-methyl-4-(methylthio)phenyl(1-methylethyl)-phosphoramidate, commercially available as the productNEMACUR 3 from Miles, Inc. (Kansas City, Mo.); other organophosphatesinclude ethoprophos, dichlofenthion, diamidafos, fensulfothion,fosthietan, isazofos and thionazin. Representative of the carbamatechemical pesticides useful in the invention is oxamyl, or methylN',N'-dimethyl-N-[(methylcarbamoyl)oxy]-1-thiooxamidimidate,commercially available as the product PRATT OXAMYL 10% G from MillerChemical & Fertilizer Corp. (Hanover, Pa.).

When applied separately, the metabolite and pesticide of the presentinvention may be administered according to their respective producthandling instructions. When applied as a composition of the presentinvention, the metabolite and pesticide can be mixed in whatever formmay be suitable (such as solution, suspension, emulsion, powder orgranular mix) and delivered to the plant or soil by hand, broadcast,in-row, drench or other means either at planting or to establishedplants. Such compositions may additionally include solvents,surfactants, emulsifiers, bulking or flow-enhancing agents, and/or otherexcipients known in the agricultural pesticide and fertilizerformulation arts, as for example the surfactant polysorbate 80 in thecase of aqueous emulsions or solutions.

Optimum rates of application of the metabolite and pesticide, for aparticular target nematode and set of conditions, can be determinedeasily and without undue experimentation by simple ranging studiescarried out in greenhouse or field settings. Based on the resultsdescribed below, it is expected that significant nematode control can beaccomplished by using 50% of the recommended rate for the metabolite andbetween 10% and 25% of the pesticide. It is further expected that theabove methods and compositions will be effective against a broad rangeof nematodes, including but not limited to Meloidogyne species such asM. incognita, M. arenaria, M. javanica and M. chitwoodi; Anguina speciessuch as A. tritici; Ditylenchus species such as D. destructor and D.dipsaci; Pratylenchus species such as P. penetrans; Heterodera speciessuch as H. glycines and H. schachtii; Aphelenchus species such as A.avenae; Radopholus species such as R. similis; Xiphinema species such asX. index; and Rotylenchulus species such as R. renifornis.

The method and compositions of the present invention will be betterunderstood in connection with the following examples, which are intendedas an illustration of and not a limitation upon the scope of theinvention. Both below and throughout the specification, it is intendedthat citations to the literature are expressly incorporated byreference.

EXAMPLE 1 Greenhouse Evaluation of Methyl Propiolate and ABG-9008

The effects of the Myrothecium verrucaria metabolite, ABG-9008, andmethyl propiolate (Aldrich Chemical Co., Milwaukee, Wis.) on rootinfestation by the root-knot nematode Meloidogyne incognita were testedas follows: Cucumber seedlings were grown, two per pot, in 2 inch (5 cm)diameter pots each containing about 125 g of a pasteurized mix of sandand soil (2:1). The plants were grown in a greenhouse maintained at 28°C. and were watered uniformly on a daily basis. On day zero, the plantswere treated with a 15 ml drench of nematocidal agent in an aqueoussolution of 0.1% polysorbate 80 (or of the solution vehicle alone),after which each pot was inoculated with 800 Meloidogyne incognitajuveniles. On day six, the plants were harvested, the roots were washed,and the number of root galls were counted under a dissecting microscope.The results for each treatment or control (n=8 plants for each) areshown below in Table 1, where the reduction in root galling is stated asa percent of the number of galls observed in untreated control plants.

These results clearly demonstrate the synergistic effect of a chemicalnematocide and the metabolite of Myrothecium verrucaria, ABG-9008; forexample, the amount of methyl propiolate producing a 5% reduction inroot galling by itself (0.75 mg per pot), when administered with anamount of ABG-9008 producing a 27% reduction in root galling by itself(0.5 g per pot), is sufficient to produce a 61% reduction in galling.

                  TABLE 1                                                         ______________________________________                                        Reduction in Root Galling of Cucumber Seedlings                                   Treatment and Rate Per Pot                                                                       % Reduction in Root Galling                            ______________________________________                                        Methyl propiolate @ 0.75 mg                                                                      5                                                            Methyl propiolate @ 1.0 mg           31                                       ABG-9008 @ 0.5 g                     27                                       Methyl propiolate @ 0.75 mg          61                                       plus ABG-9008 @ 0.5 g                                                         Methyl propiolate @ 1.0 mg           65                                       plus ABG-9008 @ 0.5 g                                                         Control (0.1% polysorbate 80)              --                               ______________________________________                                    

EXAMPLE 2 Greenhouse Evaluation of Fenamiphos and ABG-9008

The effects of ABG-9008 and the organophosphate fenamiphos on rootinfestation by Meloidogyne incognita were tested as follows: Cucumberseedlings were grown as before, but three per pot and in 5 inch (12.7cm) diameter pots each containing about 1 kg of sand/soil mix. Theplants were treated on day zero with a 120 ml drench of either anematocidal treatement or a water control solution, followed byinoculation of each pot with 1200 Meloidogyne incognita juveniles. Onday fourteen, the plants were harvested, the roots were washed, and thenumber of root galls were counted under a dissecting microscope. Theresults for each treatment or control (n=12 plants for each) are shownbelow in Table

                  TABLE 2                                                         ______________________________________                                        Reduction in Root Galling of Cucumber Seedlings                                   Treatment and Rate Per Pot                                                                       % Reduction in Root Galling                            ______________________________________                                        Fenamiphos @ 0.40 μl                                                                          0                                                            ABG-9008 @ 4.0 g                     54                                       Fenamiphos @ 0.4 μl               82                                       plus ABG-9008 @ 4.0 g                                                         Control                                   --                                ______________________________________                                    

The fenamiphos product used was NEMACUR 3 (Miles Inc., Kansas City,Miss.), the recommended label rate for which is 5.3 pints per acre (1.6μl per pot, based on surface area). The above results demonstrate thesynergy between the metabolite and the chemical pesticide of the presentinvention, in that fenamiphos applied at one-fourth the recommended rate(a rate which has no effect on nematodes), when administeredconcurrently with ABG-9008 at a rate which by itself causes only a 54%reduction in galling, is capable of reducing galling by 82%.

EXAMPLE 3 Greenhouse Evaluation of Fenamiphos and ABG-9008

The experiments of Examples 1 and 2 were repeated with cucumberseedlings planted two per pot in 2 inch (5 cm) diameter pots eachcontaining about 125 g of sand/soil mix. The plants were treated on dayzero with a 15 ml drench of either a nematocidal treatement or a watercontrol, followed by inoculation of each pot with 800 Meloidogyneincognita juveniles. On day five, the plants were harvested, the rootswere washed, and the number of root galls were counted under adissecting microscope. The results for each treatment or control (n=6plants for each) are shown below in Table 3.

                  TABLE 3                                                         ______________________________________                                        Reduction in Root Galling of Cucumber Seedlings                                   Treatment and Rate Per Pot                                                                       % Reduction in Root Galling                            ______________________________________                                        Fenamiphos @ 0.01 μl                                                                          7                                                            ABG-9008 @ 1.0 g                     90                                       ABG-9008 @ 0.5 g                     24                                       ABG-9008 @ 0.4 g                     0                                        Fenamiphos @ 0.01 μl              49                                       plus ABG-9008 @ 0.5 g                                                         Fenamiphos @ 0.01 μl              28                                       plus ABG-9008 @ 0.4 g                                                         Control                        --                                           ______________________________________                                    

The fenamiphos product used was NEMACUR 3 (Miles Inc., Kansas City,Miss.), the recommended label rate for which is 2.5 liters per acre (0.4μl per pot, based on surface area). The above results again demonstratethe synergy between the metabolite and the chemical pesticides of thepresent invention.

EXAMPLE 4 Greenhouse Evaluation of Oxamyl and ABG-9008

The effects of ABG-9008 and the carbamate pesticide oxamyl on rootinfestation by Meloidogyne incognita were tested as follows: Cucumberseedlings were grown as before, but two per pot and in 2 inch (5 cm)diameter pots each containing about 125 g of sand/soil mix. The plantswere treated on day zero with a 15 ml drench of either a nematocidaltreatment or a control (water), followed by inoculation of each pot with800 Meloidogyne incognita juveniles. On day five, the plants wereharvested, the roots were washed, and the number of root galls werecounted under a dissecting microscope. The results for each treatment orcontrol (n=6 plants for each) are shown below in Table 4.

                  TABLE 4                                                         ______________________________________                                        Reduction in Root Galling of Cucumber Seedlings                                   Treatment and Rate Per Pot                                                                       % Reduction in Root Galling                            ______________________________________                                         Oxamyl@ 1.0 mg                                                                              94                                                               Oxamyl @ 0.3 mg                      38                                       ABG-9008 @ 0.4 g                     14                                       Oxamyl @ 0.3 mg                      73                                       plus ABG-9008 @ 0.4 g                                                         Control                         --                                          ______________________________________                                    

The oxamyl product used was PRATT OXAMYL 10% G (Miller Chemical &Fertilizer Corp., Hanover, Pa.), the recommended label rate for which is35 kg per acre (13 mg per pot, based on surface area). The product wascompletely dissolved in water before treatment of the plants. The aboveresults again demonstrate the synergy between the metabolite and thechemical pesticides of the present invention.

It is understood that the foregoing detailed description andaccompanying examples are merely illustrative and are not to be taken aslimitations upon the scope of the invention, which is defined solely bythe appended claims and their equivalents. Various changes andmodifications to the disclosed embodiments will be apparent to thoseskilled in the art. Such changes and modifications, including withoutlimitation those relating to the active agents and excipients of theinvention, may be made without departing from the spirit and scopehereof.

What is claimed is:
 1. A method for suppressing plant damage bynematodes comprising the step of concurrent administration, to thelocus, soil or seeds of plants in need of such treatment, a synergisticeffective amount of(a) metabolite of the fungus Myrothecium verrucariaapplied at a rate of from about 15 to about 30 pounds per acre and (b)fenamiphos, applied at the rate of from about 0.025 to about 1.25 litersper acre.
 2. A method according to claim 1 wherein the fungus isMyrothecium verrucaria strain ATCC
 46474. 3. The method of claim 1wherein fenamiphos is administered at a rate of between about 0.025 and0.75 liters per acre.
 4. The method of claim 3 wherein said metaboliteis administered at a rate of from about 10 to about 20 pounds per acre.5. A nematocidal composition comprising:a synergistic effective amountof a metabolite of the fungus Myrothecium verrucaria applied at a rateof from about 15 to about 30 pounds per acre in combination withfenamiphos applied at the rate of from about 0.025 to about 1.25 litersper acre.
 6. A nematocidal composition according to claim 5 wherein thefungus is Myrothecium verrucaria isolate ATTCC 46474.